We have recently cloned several new members of the murine CYP2C subfamily, expressed the recombinant P450 proteins in E. coli, and showed that they are active in the metabolism of arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs) and/or hydroxyeicosatetraenoic acids (HETEs), eicosanoids that possess potent biological activities in numerous tissues. These enzymes are also active in the metabolism of linoleic acid to epoxyoctadecenoic acids (EOAs) and hydroxyoctadecadienoic acids (HODEs). The murine subfamily is very complex (consists of 15 genes and 4 pseudogenes). Despite the fact that these enzymes are 69-92% identical at the amino acid level, they differ markedly in their catalytic turnover and each enzyme has a unique product profile. RT-PCR and immunoblotting studies reveal that CYP2C mRNAs and proteins are abundant in both hepatic and extrahepatic tissues, and that the tissue and cellular distribution is P450 isoform-specific. We have developed a panel of immunospecific peptide-based antibodies to the murine CYP2C isoforms so that their tissue distribution and regulation can be further investigated. We have recently identified CYP2C29 as one of the major CYP2C isoforms in liver, intestine and adrenal. In addition to its role in the metabolism of fatty acids, this enzyme is involved in metabolism of xenobiotics such as the anticonvulsant phenytoin and is induced by phenytoin as well. We have cloned the Cyp2c29 gene, characterized its intron-exon organization, and generated Cyp2c29 null mice by conventional gene targeting strategies. The mice are healthy, fertile and exhibit no overt pathology. These mice will be studied at baseline and after selected stimuli (e.g. phenytoin administration) to determine the physiologic and pharmacologic function of this P450.